The present invention relates to stepper motor drives, and more particularly to a microprocessor stepper motor drive which is digitally controlled.
Stepper motors have been employed in the driving portion of equipment such as X-Y plotters and printers. The movable object of such equipment needs to be accelerated to a selected velocity, and then decelerated. The acceleration/deceleration profiles are either linear or nonlinear. Linear profiles, as shown in FIG. 1a, result in ringing at the inflection points of the profile. Nonlinear profiles which are optimized for a maximum velocity are truncated for lower velocities as shown in FIG. 1b, again resulting in ringing. To make nonlinear profiles suitable for several selected velocities, a plurality of profiles, one for each velocity, have been stored in a plurality of look-up tables, using excessive memory.
What is desired for a massive moving object, such as a drum on a digitizing device, is a velocity profile having a slow start, a fast rise, and then a smooth inflection to the operating velocity, which profile is the same for every final velocity desired without the need for a plurality of profile tables for each selected final velocity.